These are golden days for conspiracy theorists. If you believed your government was spying on you, Edward Snowden’s revelations have shown you’re probably right. WikiLeaks and Bradley Manning laid bare a world in which the authorities routinely do one thing and say another. You may be paranoid, but they’re still out to get you — or at least to detain you at Heathrow Airport for questioning.

Now, just a week shy of 16 years since a Mercedes plowed into a pillar in the Pont de l’Alma tunnel on Aug. 31, 1997, depriving Britain of her People’s Princess and the young royals William and Harry of their mother, along comes a fresh allegation in the story that has generated more conspiracy theories than any other. Scotland Yard announced on Saturday that it is “scoping” new information about the Paris car crash that killed Diana, Princess of Wales and patron saint of conspiracy theorists. The claim surfaced during the trial of a member of Britain’s elite and secretive SAS army regiment; according to some reports, the estranged in-laws of a key witness told the military police that the witness had alleged SAS involvement in Diana’s death.

The circumstances of that death, though, have been exhaustively investigated, by the authorities in France and the U.K., most recently in the 90-day inquest at London’s Royal Courts of Justice that reached the conclusion in April 2008 that the Princess and her boyfriend Dodi Fayed had been “unlawfully killed.” The verdict highlighted the “gross negligence” of the driver Henri Paul, who died at the wheel and was found to have blood alcohol three times above the French legal limit, and of the paparazzi, whose reckless pursuit of the couple sparked the high-speed chase that ended in tragedy. But no matter how deep the probes or how expensive — the cost to British taxpayers of the police inquiry and inquest is estimated to have topped $20 million — skeptics continued to raise questions and rumors to swirl.

A quick Internet search reveals a plethora of sites devoted to “exposing” Diana’s murder. A large and vociferous online community remains convinced, despite evidence to the contrary presented to the inquest, that the Queen’s former daughter-in-law was pregnant with Fayed’s child, provoking nebulous rings of vested interest at the heart of the British establishment into ordering her assassination to protect the monarchy. The more lurid versions of the tale claim the crash itself never happened (the Mercedes was dented in a car crusher; the Princess hijacked in the tunnel, forced into a vehicle masquerading as an ambulance and slaughtered). A surprisingly persistent meme depicts Diana as the victim of giant shape-shifting lizards that secretly control Britain. There are queries raised too about how and when a white Fiat Uno came into contact with the Mercedes, leaving paint traces, or whether Paul’s blood toxicology tallies with what is known of his last movements and usual habits, or why Diana’s seat belt was found not to work.

These queries seem sensible enough, and if we’ve learned anything from the whistle-blowers, hackers and leakers, it’s that the authorities don’t always tell the truth. But we knew that already. We may be in greater danger of forgetting that the authorities often do tell the truth too. Sometimes things are exactly as they seem: President Obama was born in Hawaii and Diana died in an accident, a victim not of unseen malefactors but of a collision between her desire for a private life and public fascination with her private life.

Scotland Yard — itself seeking to restore public trust after the twin blows of the News Corp phone-hacking scandal and the Jimmy Savile sex-abuse revelations revealed its tendency to protect the establishment rather than question it — has no choice but to evaluate the information it has received. To fail to do so would spark new conspiracies. Yet to divert more taxpayer money into a new inquiry also risks criticism. Hence the Yard’s carefully worded statement, issued on Saturday night, which made clear: “This is not a reinvestigation.” Die-hard Diana conspiracists will be disappointed. They will always be disappointed.